Auyuittuq National Park, on Baffin Island in northern Canada, is one of the world’s last great unexplored wildernesses. Few have conquered it. Even fewer can spell it. With an Inuit name meaning “the land that never melts,” Auyittuq is full of stunning fjords and majestic peaks—like Mount Asgard, the cliff that James Bond leaps from using a Union Jack parachute at the beginning of The Spy Who Loved Me. But believe it or not, Mount Asgard isn’t the park’s scariest summit. That honor belongs to nearby Mount Thor, the world’s tallest cliff.

Mount Thor is named for the Norse god of thunder, and believe me, it might just take an act of divine intervention (or Marvel Comics superpowers) to get to the top. The peak’s west face is the longest vertical drop on Earth: 4,101 feet (the better part of a mile!) straight down. Actually, the slope is steeper than vertical, since the face is actually a 105-degree overhang.

As you might imagine, a sheer 4,000-foot rock face is no picnic to climb. More than 30 attempts to scale Thor met with failure before a four-man American team finally completed the climb in May 1985. The team faced nonstop dangers from falling rocks to dwindling supplies—even though they brought over half a ton of food, gear, and fuel up the cliff with them. The ascent took them 33 days!

Mount Thor is a popular site for BASE jumpers and paragliders hoping to get the ultimate rush by throwing themselves off the world’s tallest cliff (presumably after slamming a Mountain Dew). But Auyuittuq Park has a unique jumping ban, due to the difficulty of getting emergency crews to the remote location, so Canada routinely prosecutes thrill-seekers dumb enough to take the shortcut back down to base camp.

If you’ve conquered the world’s tallest vertical cliff and are looking for new challenges, head to Baltistan, in northern Pakistan. The east face of the Great Trango Tower there is the world’s tallest near-vertical cliff: not as sheer as Thor, but three hundred feet taller. The first expedition to scale Trango’s east face, in 1984, died on the descent, and it’s still widely considered to be the world’s toughest big-wall climb.